Current development in the field of universal joints is primarily directed toward improving performance of the universal joint by increasing the torque transmitting capability of the universal joint and reducing noise and vibration of the universal joint. The improved performance of the universal joint has resulted in an increased cost to manufacture the universal joint. However, there is still a demand for inexpensive and easily produced universal joints.
U.S. Pat. No. 4,832,657 (the '657 patent) discloses such an inexpensive and easily produced universal joint. The universal joint comprises an outer member. The outer member defines an interior opening and a plurality of grooves extending along a longitudinal axis and disposed within the interior opening. Each of the grooves is parallel to all other of the grooves and the longitudinal axis and includes a straight linear profile along the longitudinal axis. An inner member is disposed within the interior opening and defines a plurality of apertures extending radially outward from the longitudinal axis with each of the apertures opposing one of the grooves. The inner member further defines a center bore concentric with the longitudinal axis and extending through said apertures. The universal joint further comprises a plurality of drive balls having a spherical shape. One of the drive balls is supported by and rotatable within each of the apertures, and supported by one of the grooves in rolling engagement. A center pin is disposed within the center bore and engages the drive balls in rolling engagement. However, the universal joint disclosed in the '657 patent does not include a structure preventing the drive balls disposed between the apertures and the grooves from rattling therebetween as the inner member articulates relative to the outer member, thereby creating undesirable noise and vibration.
U.S. Pat. No. 6,685,571 (the '571 patent) also discloses such an inexpensive and easily produced universal joint. The universal joint comprises an outer member. The outer member defines an interior opening and a plurality of grooves disposed within the interior opening. The grooves extend along a longitudinal axis. An inner member is disposed within the interior opening and defines a plurality of pockets. The pockets are disposed radially about the longitudinal axis with each of the pockets opposing one of the grooves. The universal joint disclosed in the '571 patent further comprises a plurality of drive balls having a spherical shape. One of the drive balls is supported by and rotatable within one of the pockets, and supported by one of the grooves in rolling engagement. Each of the grooves includes a curved profile along the longitudinal axis to keep the drive balls in contact with the groove while the universal joint is articulated.
While these universal joint designs may be useful, there remains a need for universal joints having improved performance characteristics, particularly improved torque transmitting capability and reduced noise and vibration, which can be readily manufactured for a low cost relative to other universal joint designs.